3 Answers
3

The part about mencoder that you want is the parameter -vop scale which tells mencoder to what scale you want the video to go to. This is normal if you want to reduce bandwidth use, lower video size, etc..

Scale = Parameter to scale to. In this case you are dividing the original size by 2 (iw/2)

both of which can provide more information if you either execute them without parameters or variables like just mencoder or ffmpeg or type for example man mencoder or man ffmpeg which will give you a VERY extensive little manual on how to work with them.

@artfulrobot Correct. Had to set it to transcode first. +1
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Luis Alvarado♦Dec 11 '12 at 12:26

On Ubuntu Precise: avidemux gives warnings about h264 saying that you'll either lose frame accuracy, or get stuttering/crashes. avconv took over an hour on my Intel i5 to process a 13 minute file and generated a much bigger file than the original. I can't get mencoder to work Cannot find codec 'mp4' in libavcodec Couldn't open video filter 'lavc'. Openshot doesn't give much control (bunch of presets, none are what I needed) over output and created files that played at the wrong speed or had choppy audio. :-(
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artfulrobotDec 11 '12 at 13:17

@artfulrobot - Wow you got problems ^^. Avidemux does say the warnings over h264 because you WILL loose frame accuracy (Not much crash)when transcoding, the only way would be to actually put the same compression/rate/bits/etc.. For the avconv time there has to be a problem. I did a 1 hour 23 minute movie in mp4 format with h264 in about 25 minutes with an i3. With an i7 2600 it went down to 11 minutes. Did you happen to install the restricted extra package
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Luis Alvarado♦Dec 11 '12 at 13:40

I tried avconv. It is giving me command not found. I tried everything mentioned above. It is giving me the same answer. It would be really useful if you could suggest an alternate solution.
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thejaJul 10 '12 at 12:04